The emission of Ga+ ions and neutral Ga0 atoms, induced by the irradiation of (110) surfaces with laser pulses of sub-bandgap energies, were measured. It was found that the Ga+ yield of partially annealed Ar+ ion-bombarded surfaces was reduced by thermal annealing, and also by repeated irradiation with laser pulses, while the Ga0 yield was not affected to any great extent by these treatments. The Ga+ emission, which occurred at a lower fluence than Ga0 emission, was traced to defect sites at surfaces. It was suggested that measurements of the laser-induced particle emission for sub-bandgap energies could be useful for the detection and elimination of low-density defects on surfaces.

Y.Nakai, K.Hattori, N.Itoh: Applied Physics Letters, 1990, 56[20], 1980-2